Esophageal strictures in humans can result from a number of causes, both disease and injury related. For example, scar tissue from corrosive injury can cause esophageal stricture, as can cancer, esophagitis, hernia, and cardiospasm, among other causes. These esophageal strictures prevent the normal functioning of the esophagus and can impede a person's ability to swallow and/or block digestive tract access. Treatment for esophageal strictures often involves mechanical dilation by some type of dilator, typically inserted through a patient's mouth.
Mechanical dilators have traditionally fallen into one of three general types. A first type is a tapered "bougie" with a hollow central channel which accommodates a positional guide wire, one end of which has been previously placed in the patent and fed through the esophageal opening. The opposite end of the guide wire is inserted into the central channel of the bougie and the bougie is fed into the patient via the guide wire until the bougie encounters the esophageal stricture. Since the bougie tapers outward, additional pressure on the bougie acts to dilate the stricture. Depending upon the degree of closure, several treatments with increasingly larger bougies may be necessary.
A second type is a balloon dilator which is similarly positional guide wire guided into the patient until the balloon portion of the dilator is positioned in the esophageal opening. The balloon is then slowly inflated, thus putting outward pressure on the esophageal stricture.
Finally, a third category is a Mercury filled bougie, traditionally made of a tapered rubber sheath which is filled with Mercury. The combined flexibility and rigidity achieved by the sheath and the Mercury, as well as the weight of the Mercury allows the bougie to be dropped into position through the patient's mouth and down to the esophageal stricture. Mercury filled bougies have lost favor recently because of the threat of Mercury poisoning from Mercury leaching through cracks in the bougie rubber sheath. Furthermore, Mercury filled bougies can be accidently misdirected into a patient such that they can impact and damage unintended portions of the gastrointestinal tract. In one recently developed dilator, Tungsten particles suspended in a silicone material have been substituted for the Mercury in a bougie, as is taught in U.S. Pat. No. 5,366,471 to Richard G. Jones, et al.
A typical first step of an attending physician with a patient with an esophageal stricture is to insert an endoscope into the esophagal opening in order to estimate the diameter of the stricture. A properly sized dilator is then selected to enlarge the stricture diameter by one or two "French" sizes. A French size is based upon the circumference of the stricture (or dilator) in millimeters.
It is common for all three types of mechanical dilators to include at least some portion which is radiopaque such that they can be used in conjunction with fluoroscopy equipment to accurately locate and diagnose the stricture as well as allowing the attending physician to reliably direct the dilator to the proper place. This prevents the misdirection of the dilator and allows the attending physician to accurately gauge the stricture position.
Prior art mechanical dilators were very expensive due to required exacting manufacturing tolerances, the need to make the bougie at least partially radiopaque and the use of expensive fillers such as Mercury or Tungsten. Due to their high costs, these dilators are typically reused, often for years. This presents serious sterilizing problems, particularly for bougies with hollow central guide wire channels, which are almost impossible to get completely sterile after use. Furthermore, prior art bougies are tapered outward from a tip to a single French size, typically anywhere from 28 to 60 French in circumference. Thus, when multiple dilation insertions with increasingly larger bougies are required, the attendant expense and sterilization problems for each bougie are considerably multiplied. Additionally, each insertion of a different bougie increases throat trauma, and, with guide wire directed dilators, increases the chances of kinking the guide wire within the patient.
An additional problem with prior art dilators is the increasing stiffness of the dilator bougies as size, i.e. working circumference, increases. This makes passage of the bougies through the patient's throat area increasingly more difficult as the size increases since the stiffer bougies do not bend as easily.
It is clear, then, that a need exists for an improved esophageal dilator which avoids the problems attendant in the prior art. Such an improved dilator should preferably be inexpensive enough to be disposable after a single use to avoid sterilization problems, should also minimize the number of insertions required for a dilation treatment, and dilator bougies should be consistent in flexibility over the range of sizes.